Neuronal basis of behavior by Hana Brozka “Man can do what he wills but he cannot will what he wills.” ― Arthur Schopenhauer, Essays and Aphorisms Outline • What is behavioral neuroscience? • Tools to study neuronal basis of behavior • Behavioral tools • Tools to modify neuronal activity/function • Tools to observe neuronal activity • Pitfalls of current methods in behavioral neuroscience • Innate behaviors • Feeding • Aggression • Parental behaviour • Vocalizations – signaling emotional state • Goal directed (motivated) behaviors (Action‐Outcome; Stimulus‐Response) • Habit fomation ‐ basal ganglia anatomy and function • Stereotypical behaviors What is behavioral neuroscience? • is the study of the biological basis of behavior in humans and animals • covers a range of topics, including genetic, molecular and neuroanatomic substrates of behaviour. • Studies the interaction between the brain, body, environment and behaviour • Behavioural vs cognitive neuroscience: behavioural pertains to movement, cognitive to mental processes Tools to study neuronal basis of behavior • Behavioral tools • Mazes • Operant tasks (reinforcement and punishment) • Observation of free movement • Tools to interfere with normal brain function • Administration of agonist/antagonists (systemic, localized) • Lesions (permanent neuronal ablation) • Inactivation (temporary) • Optogenetics (increase decrease activity ‐ localized) • Chemogenetics (increase decrease excitability – both localized and systemic) • Genetic models (knock outs, inducible knockouts (dox on dox off) • Transcranial magnetic stimulation (TMS) • Tools to observe undisturbed brain activity • Immediate early genes • Electrophysiology • Calcium imaging • MRI, PET, EEG Pitfalls of presently used tools in behavioral neuroscience • Behavioral tests: • Rarely test assesses only one behavioral ‘entity’ (differential state of attention, anxiety, motivation, arousal all can impact a results of the study) = difficult to isolate a single process of interest • Usually only a single parameter is selected. If more parameters are selected usually inapproprate statistical methods are used (MANOVA = right; many separate ANOVAs = wrong ‐ increases posibility of false positives (type 1 error) and disregards relationships between output variables) • Interferance with normal brain function: • Chronic inactivation of brain regional activity/genetic models: compensatory mechanisms may develop (both behavioral and neuronal). • Genetic models are ok when they are genetic model of geneticaly based disease (because, persumably, the same compensatory mechanisms are present in patients as well) • Acute administration of agonists/antagonist inactivations/facilitations of brain regional activity (muscimol, optogenetic, chemogenetic): altered state can divert atttention of the animal (‘feeling stange’) ‐ habituation to the manipulation prior to the experiment is therefore essential • Observation of neuronal activity: • IEG expression: only neurons that undergo neuroplastic changes are stained, very low temporal resolution • Limitations: • Electrophysiology: relatively small areas can be observed at the same time (but very good temporal and spatial resolution) • Calcium imagining: larger areas can be explored, with worse temporal resolution (compared to electrophysiology) deep structures are more difficult to asess (GRIN lens inplantation is needed) • MRI, PET ‐ generally low temporal and spatial resolution in rodents ‐ but you can record whole brain • PET, EEG ‐ low spatial resolution, EEG ‐ good temporal resolution • TAKE HOME: do not trust every experiment that you read about Innate behaviors • Innate behaviors do not require learning (feeding, defence, parental care, sociability in social species) • ‘instinct’ • Appears in fully funtional form the first time, and are expressed even when the animal is raised in isolation • Important in survival of the individual and propagation of species • Innate behaviors are complex • Species‐specific • Hypothalamus is essential for expression of innate behaviors (four F’s”: fighting, fleeing, feeding, and mating) • Below thalamus ‐ bottom of the brain • More than 20 nuclei • Integrates signals from periphery and from CNS • More permeable BBB than other brain regions • Before advent of molecular techniques hypothalamus was difficult to study: nuclei are very interconected and each nuclei contains different types of neurons responsible for different functions‐ more selective methods avaliable in the last decade • Common principles: integratory hub, redundancy and neuronal population with antagonistic function withing the same nucleus (recieve same inputs, project to same areas but use different neurotransmitter to convey opposite signal) • Antagonistic control is a common theme to maintain homeostatis (sympaticus vs parasympaticus – same organs are innervated and different neurotransmitters convey opposite signal, insuline vs glucagon, postural stability: biceps v. triceps). Helps to maintaining state of the animal within narrow homeostatic range Feeding • Nutrient intake is essential and requires food seeking and consumption behaviors • There is a evolutionary pressure on feeding behavior and it is expected to be ‘hard‐ wired’ • Hypothalamus: patients with hypothalamic injuries/tumors displayed rapid onset obesity • In animals, damage to VMH and PVN led to obesity • VMH/PVN = ‘satiety centres’; • In animals, damage to LH led to anorexia • LH = ‘hunger centre’ Feeding ‐ external signals • Leptin (adipose tissue) • Ghrelin (released from empty stomach) • Glucose • Insulin Feeding – Agrp and α‐MCH neurons of Arcuate nucleus • Arcuate nucleus ‐ leptin receptors (but aslo ghrelin, glucose and isulin receptors) • Two groups of neurons: one group releases Agouti related peptide (Agrp) ‐ consumption other Melanin‐concentrating hormone alpha (α‐MCH) ‐ satiety • No lepn → Agrp neurons acve → consumpon (leptin has inhibitory effect on Agrp neurons) • Smell of food also activated Agrp neurons ‐ this means that Agrp neurons are also under neuronal control • Agrp neurons are inhibitory and release neuropeptide Y and GABA • In adults optogenetic inhibition of Agrp neurons supressed feeding in starved animals • Optognetic activation induces food foraging in satiated animals • Lepn → α‐MCH neurons active → saety (leptin has excitatory effects α‐MCH neurons) • α‐MCH, releases from Arcuate α‐MCH neurons activates melanocortin receptors and supresses feeding Feeding – Agrp neurons and their downstream targets • Agrp neurons project to paraventricular nucleus of hypothalamus (PVN), orexigenic neurons in LH (lateral hypothalamic area LHA) and locally to α‐MCH neurons of Arcuate nucleus • LHA neurons release orexin. Lesion of LHA leads to starvation of animals • And to parabrachial nucleus (BPN) Feeding – anorexia circuit • Normaly Agrp neurons inhibits para‐brachial nucleus (PBN) • PBN receives visceral and taste information from the periphery (via nucleus of the solitary tract (NTS)) • PBN signals malaise and illness of GIT • When Agrp neurons are ablated, cFos expression in PBN is elevated. (and animal feels sick) • Injection of benzodiazepines into PBN rescues feeding behavior • Therefore, PBN actively supresses feeding behavior, but during hunger it is supressed by Arcuate nucleus • In intact mice ablating BPN increases feeding behavior Aggressivity • Innate behavior with the purpose to protect, secure resources and ensure societal status • Regulated by environmental, hormonal, and experiential factors • Observed mostly in males except for lactating females • Resident‐intruder test • Intermale agressivity • Follows a stereotyped escalating pattern until one combatant assumes a submissive position • Serves to establish interindividual hierarchy • Perisitence upon removal of the stimulus – hysteresis • Associated with rewarding properties • Maternal aggression • Hormonal changes and exteroceptive stimulation by pups • Male aggressivity towards pups • Virgin males • Submissive behavior Aggressivity ‐ main agressivity hub: MEA‐ PMv‐VMHvl • Medial amygdala (MEA) recieves olfactory input • ventral premammillary nucleus (PMv) processes sensory information related to agression; only neurons that express dopamine transporter (but do not synthetize dopamine) • Optogenetic activation of PMv triggers attack, optogenetic silencing PMv terminates attack • Projects to ventromedial hypothalamus VMHvl • optogenetic activation of VMHvl neurons induces immediate attacks in males, while chemogenetic inhibition of VMHvl neurons decreases normal aggression • Both PMv and VMHvl can drive agression without sensory input • In males, only optogenetic activation of PMv, VMHvl neurons that express estrogen receptor alpha triggers attack. In females opto activation of same neurons does not induce agression. (Estrogen receptor alpha is a transcription factor). • Highlights importantce of sex hormones in aggressive behavior and intersex differences in expression of agressivity Aggressivity ‐ inputs and outputs from the main agressivity hub • Inputs: • posterior amygdala (PA) is an upstream regulator of MEA and recieves input from ventral hippocampus and vomeronasal organ • Vomeronasal organ is important in gender identification • Lesion of vomeronasal organ reduces aggressively • PA processes input and relays signal to MEA, VMHvl (in case of agression, glutamate releasing neurons). • Again, PA neurons that process this information highly express estrogen receptor alpha • Outputs: • VMHvl projections to ventral portion of